330 



NA TURE 



[August 5, 1897 



gas finds its way out with a rush so overpowering as to score a 

 wide channel in the metal ; some of these stoppers and vents 

 are on the table. To illustrate my argument Sir Andrew 

 Noble has been kind enough to try a special experiment. 

 Through a cylinder of granite is drilled a hole 0"2 inch 

 diameter, the size of a small vent. This is made the stopper 

 of an explosion chamber, in which a quantity of cordite is fired, 

 the gases escaping through the granite vent. The pressure is 

 about 1500 atmospheres, and the whole time of escape is less 

 than half a second. Notice the erosion produced by the 

 escaping gases and by the heat of friction, which have scored 

 out a channel over half an inch diameter and melted the granite 

 along their course. If steel and granite are thus vulnerable at 

 comparatively moderate gaseous pressure, is it not easy to 

 imagine the destructive upburst of hydrogen and water-gas 

 grooving for itself a channel in the diabase and quartzite, tear- 

 ing fragments from resisting rocks, covering the country with 

 debris, and finally, at the subsidence of the great rush, filling 

 the self-made pipe with a water-borne magma in which rocks, 

 minerals, iron oxide, shale, petroleum, and diamonds are 

 churned together in a veritable witch's cauldron ! As the heat 

 abated the water vapour would gradually give place to hot 

 water, which forced through the magma would change some of 

 the mineral fragments into the now existing forms. 



Each outbreak would form a dome-shaped hill, but the 

 eroding agency of water and ice would plane these eminences 

 until all traces of the original pipes were lost. 



Actions, such as I have, described, need not have taken place 

 simultaneously. As there must have been many molten masses 

 of iron with variable contents of carbon, different kinds of 

 colouring matter, solidifying with varying degrees of rapidity, 

 and coming in contact with water at intervals throughout long 

 periods of geological time — so must there have been many out- 

 bursts and upheavals, giving rise to pipes containing diamonds. 

 And these diamonds, by sparseness of distribution, crystalline 

 character, difference of tint, purity of colour, varying hardness, 

 brittleness, and state of tension, would have impressed upon 

 them, engraved by natural forces, the story of their origin — a 

 story which future generations of scientific men may be able to 

 interpret with greater precision than we can today. 



Who knows but that at unknown depths in the earth's 

 metallic core beneath the present pipes there are still masses 

 of iron not yet disintegrated and oxidised by aqueous vapour 

 — masses containing diamonds, unbroken, and in greater pro- 

 fusion than they exist in the present blue ground, inasmuch 

 as they are enclosed in the matrix itself, undiluted by the 

 numerous rock constituents which compose the bulk of the 

 blue ground. If this be the case a careful magnetic survey of 

 the country around Kimberley might prove of immense interest, 

 scientific and practical. Observations, at carefully selected 

 stations, of the three magnetic elements — the horizontal com- 

 ponent of direction, the vertical component of direction, and 

 the magnetic intensity — would soon show whether any large 

 masses of iron exist within a certain distance of the surface. It 

 has been calculated that a mass of iron 500 feet in diameter 

 could be detected were it ten miles below the surface. A 

 rnagnetic survey might also reveal other valuable diamantiferous 

 pipes, which owing to the absence of surface indications would 

 otherwise remain hidden. 



Meteoric Diamonds. 



There is another diamond theory which appeals to the fancy. 

 It is said that the diamond is a direct gift from heaven, con- 

 veyed to earth in meteoric showers. The suggestion, I believe, 

 was first broached by A. Meydenbauer ( Chemical News, vol. 

 Ixi. p. 209, 1890), who says : — "The diamond can only be of 

 cosmic origin, having fallen as a meteorite at later periods of 

 the earth's formation. The available localities of the diamond 

 contain the residues of not very compact meteoric masses which 

 may, perhaps, have fallen in historic ages, and which have 

 penetrated more or less deeply, according to the more or less 

 resistant character of the surface where they fell. Their remains 

 are crumbling away on exposure to the air and sun, and the 

 rain has long ago washed away all prominent masses. The 

 enclosed diamonds have remained scattered in the river beds, 

 while the fine light matrix has been swept away." 



According to this hypothesis, the so-called volcanic pipes are 

 simply holes bored in the solid earth by the impact of monstrous 

 meteors— the larger masses boring the holes, while the smaller 

 masses, disintegrating in their fall, distributed diamonds broad- 



NO. 1449, VOL. 56] 



cast. Bizarre as such a theory may appear, I am bound to say 

 there are many circumstances which show that the notion of the 

 heavens raining diamonds is not impossible. 



In 1846 a meteorite fell in Hungary (the " Ava meteorite") 

 which was found to contain graphite in the cubic crystalline 

 system. G. Rose thought this cubic graphite was produced by 

 the transformation of a diamond. Long after this prediction 

 was verified by Weinschenk, who found transparent crystals in 

 the Ava meteorite. Mr. Fletcher has found in two meteoric 

 irons — one from Youndegin, East Australia, and one from 

 Crosby's Creek, United States — crystals absolutely similar to 

 those in the Ava meteorite. 



In 1886 a meteorite falling in Russia contained, besides other 

 constituents, about i per cent, of carbon in light grey grains, 

 having the hardness of diamond, and burning in oxygen to 

 carbonic acid. 



Daubree says the resemblance is manifest between the 

 diamantiferous earth of South Africa and the Ava meteorite, of 

 which the stony substance consists almost entirely of peridot. 

 Peridot being the inseparable companion of meteoric iron, the 

 presence of diamonds in the meteorites of Ava, of Youndegin, 

 and of Crosby's Creek, bring them close to the terrestrial 

 diamantiferous rocks. 



Hudleston maintains that the bronzite of the Kimberley blue 

 ground is in a condition much resembling the bronzite grains ot 

 meteorites ; whilst Maskelyne says that the bronzite crystals of 

 Dutoitspan resemble closely those of the bronzite of the meteor 

 of Breitenbach, but are less rich in crystallographic planes. 



But the most striking confirmation of the meteoric theory 

 comes from Arizona. Here, on a broad open plain, over an 

 area about five mjles diameter, were scattered one or two 



Fig. 6. — Diamond from the Canyon Diablo meteorite. 



thousand masses of metallic iron, the fragments varying in 

 weight from half a ton to a fraction of an ounce. There is 

 little doubt these masses formed part of a meteoric shower, 

 although no record exists as to when the fall took place. 

 Curiously enough, near the centre, where most of the meteorites 

 have been found, is a crater with raised edges three-quarters of 

 a mile in diameter and about 600 feet deep, bearing exactly the 

 appearance which would be produced had a mighty mass of 

 iron or falling star struck the ground, scattered in all directions, 

 and buried itself deep under the surface. Altogether ten tons 

 of this iron have already been collected, and specimens of the 

 Canyon Diablo meteorite are in most collectors' cabinets. 



An ardent mineralogist, the late Dr. Foote, in cutting a section 

 of this meteorite, found the tools were injured by something 

 vastly harder than metallic iron, and an emery-wheel used in 

 grinding the iron had been ruined. He examined the specimen 

 chemically, and soon after announced to the scientific world that 

 the Canyon Diablo meteorite contained black and transparent 

 diamonds. This startling discovery was afterwards verified by 

 Profs. Friedel and Moissan, who found that the Canyon Diablo 

 meteorite contained the three varieties of carbon— diamond 

 (transparent and black), graphite, and amorphous carbon. Since 

 this revelation, the search for diamonds in meteorites has 

 occupied the attention of chemists all over the world. 



I am enabled to show you photographs of true diamonds 

 I have myself extracted from pieces of the Canyon Diablo 

 meteorite, five pounds of which I have dissolved in acids for 

 this purpose — an act of vandalism in the cause of science for 



